This invention relates to a method of and means for producing power utilizing the flow of air in a high chimney as established by a pressure head across the chimney.
One way to establish the required pressure head is to heat the air in the lower portion of the chimney thereby decreasing its density and causing it to rise to the top of the chimney, the air flow being passed through a turbine to convert the kinetic energy of the air to useful work. Conventionally, solar energy or waste heat is utilized for heating the air. This approach is well known but has not formed the basis of a practical power generating system because the efficiency of the resultant system is relatively low requiring large amounts of heat to obtain small amounts of work.
Another way to establish the required pressure head is to cool the air in the chimney increasing its density and causing it to fall through an air turbine at the base of the chimney. This technique is illustrated in U.S. Pat. No. 3,894,393 which discloses spraying water into a chimney near the top thereof thereby evaporating the water and affording a particularly simple way of cooling the air. While the above-identified patent indicates a rather startling efficiency and power output can be obtained, the fact is that the analysis in the patent fails to take into account the drag loss of the duct on the air flow, and fails to relate the maximum exit velocity to the pressure head. A more complete analysis of the device shown in the patent reveals that the drag loss will be far in excess of the useful power that can be generated and the exit velocity of the air will be an order of magnitude less than that computed in the patent. Consequently, this technique has not found practical application in generating power.
Despite the long-term existence of the techniques described above, and despite the present need for non-fossil fuel power generation, the above-described practical difficulties with these techniques have prevented their utilization even on a small scale. It is therefore an object of the present invention to provide a new and improved system utilizing a high chimney of the type described above which overcomes or substantially reduces the difficulties and disadvantages of the prior art.